The No. 6 dry cell was one of the first batteries to replace the “wet cell” or “dangerous glass jar of liquid chemicals”, as they were called in the olden days. This site has some great info about their history (they were used to power early telephones, for example), and some different designs for repacking or remaking your own using modern D-cells.

John Edgar Park likes to make things and tell people about it. He works in CG animation at DisneyToon Studios and writes for Make, Boing Boing, and other places online and in print. You can find him at jpixl.net and twitter @johnedgarpark — if you like that sort of thing.